Dependence of blood indices of selenium and mercury on estimated fish intake in a national survey of British adults.

Objective: Contributions of fish and other foods to variance of selenium and mercury status were studied in British adults. Setting and design: Plasma and red-cell selenium and whole-blood mercury concentrations were measured during the National Diet and Nutrition Survey of Adults aged 19-64 years in mainland Britain, 2000-2001 (n = 1216). Food intake was weighed for seven consecutive days, and foods were combined in groups for data analysis. Four subsidiary groups characterised fish intakes: fried white fish, 'other' white fish, shellfish and oily fish. Results: Geometric means and 5-95% ranges were: for whole-blood mercury, 5.61 (1.30-22.2) nmoll -1 ; for plasma selenium, 1.09 (0.83-1.43) μmoll -1 ; for red-cell selenium, 1.64 (1.14-2.40) μmoll -1 . Twenty-eight per cent had no fish intake recorded during 7 days; the remaining 72% had a median intake of 237 g over the 7-day period, 5-95% range 45-780 g. Total fish intake was strongly and directly correlated with blood mercury, and moderately with red-cell and plasma selenium. Thus, sqrt(total fish intake) was correlated with: loge(blood Hg), t = +19.7; loge(plasma Se), t= +9.8; and loge(red-cell Se), t = +9.6, all P< 0.0001. All three biochemical (mercury and selenium) indices were strongly correlated with oily fish intake, and moderately correlated with shellfish and 'other' ( = non-fried) white fish, but none was significantly correlated with fried white fish. Blood mercury was strongly and directly correlated with red-cell and plasma selenium, and both increased with age. Conclusions: Dietary fish, especially oily fish, is a strong predictor of blood mercury and selenium in British adults.